In patients suffering from heart failure which may, for example, be caused by a myocardial infarction, a dilatative or ischemic cardiomyopathy or another disease, the capability of the heart to pump blood through the patient's circulatory system may be reduced to a large extent. Hence, blood supply to vitally important organs may be reduced, which may directly or indirectly lead to death of the patient.
Heart failure may be treated by means of a heart transplantation, wherein the patient's heart is replaced by a donor heart which is obtained from a brain dead person. Transplant organs, however, may be rare, and a careful selection of the transplant organ is required in order to avoid a rejection of the transplant organ by the immune system of the patient. Hence, a considerable amount of time may pass until a transplant organ suitable for the patient can be found, which amount of time may be too long to save the patient's live. More than 50% of the candidates for a heart transplantation die while they are registered on the waiting lists for a heart transplantation. Furthermore, there are many contraindications for heart transplantation such as old age, infections and longstanding high pulmonary pressure.
Therefore, it has been proposed to replace or assist the patient's heart by mechanical devices, at least temporarily while the patient is waiting for a suitable donor (“bridge to transplant”). Besides artificial hearts, which are designed to completely replace the patient's heart, cardiac assist devices have been proposed which support the action of the native heart.
In one example of a cardiac assist device according to the state of the art, an atrium of the patient's heart may be cannulated, and the cannula may be connected to a pump. Thus, blood can be pumped out of the atrium, and may be injected into a further cannula connected to an artery of the patient, wherein the artery chosen depends on whether the left or the right ventricle is supported by the cardiac assist device. The right ventricle of the heart may be supported by cannulating the right atrium and the pulmonary artery. The left ventricle may be assisted by cannulating the left atrium and the aorta.
A problem of cardiac assist devices according to the state of the art is that connecting the cardiac assist device to the circulatory system of the patient may require open heart surgery, which may imply a high risk of complications.
WO 00/35515 discloses an intravascular cardiac assist device that comprises an elongated tubular member adapted for insertion into a blood vessel, such as a pulmonary artery, the tubular member comprising a lumen defining a perfusion path within the vessel through the tubular member, an inlet port, an outlet port, an optional inlet valve associated with the inlet port and an optional outlet valve associated with the outlet port, and an inflatable member positioned in the lumen and selectively movable between a deflated position and one or more inflated positions during which blood is propelled from the inlet port axially through the lumen and back into the vessel through the outlet port and the optional outlet valve. The device is implanted through an incision in the blood vessel, and fluid is supplied to the inflatable member by means of a flexible inflation/deflation lumen inserted through the incision.
A problem of the intravascular cardiac assist device disclosed in WO 00/35515 is that the incision in the blood vessel, which is required to inflate and deflate the inflatable member, limits the application of the device to providing cardiac assist during heart surgery, and for providing post-operative support. However, the device is not suitable for providing cardiac assist for a longer period of time, for example until a donor heart for the patient is available.
WO 00/53240 discloses a balloon pump system including a catheter-mounted pumping balloon configured to be positioned within a desired body passageway to pump a fluid, for example blood, through the body passageway. A stent is percutaneously deployed within the body passageway. The pumping balloon is percutaneously deployed within the stent such that the stent is interposed between the pumping balloon and the walls of the body passageway.
A problem of the system disclosed in WO 00/53240 is that the pumping balloon provides an obstacle to fluid flow through the body passageway, even if the balloon is in its deflated state. Moreover, in the deflated state of the balloon, the balloon may have an irregular surface. Thus, turbulences may be created in the blood flow, which may lead to the formation of thrombi. It has been observed that the formation of thrombi may start within about 24 hours after the implantation of a balloon pump, and may lead to a significant risk of complications within about two weeks after the implantation of the balloon pump. Such complications may include peripheral thrombosis, infections, dysfunctions of the balloon pump, and embolism. Therefore, the device of WO 00/53240 may be used only for a relatively short period of time in exceptional situations.
It is an object of the present invention to provide a cardiac assist device which may assist the patient's heart, and which may be used without there being a requirement of open heart surgery for implantation of the device.
It is a further object of the present invention to provide a cardiac assist device which may be used for a relatively long period of time for providing a bridge to transplant, and for providing cardiac assist for an extended period of time to patients wherein counterindications such as old age, infections and longstanding high pulmonary pressure make a heart transplant difficult or almost impossible.